Thesis title: Identification of sex-specific markers affecting the immune response to influenza vaccination in healthcare workers
Health care workers face higher risk of infectious exposure due to frequent patient interactions.
Influenza vaccine is crucial for protection; however, immune responses differ by sex, affected by
hormonal and demographic factors. Understanding these differences is essential for formulating
sex-specific immunisation methods to enhance vaccine efficacy and occupational health. This study
investigated sex-based differences in immunological responses to the 2023–2024 seasonal influenza
vaccination among healthcare workers. Seroconversion and post-vaccination antibody titres were
examined in connection to sex hormones, age, comorbidities, and vaccination history to determine
factors affecting vaccine-induced immunity. A prospective longitudinal study was performed with
165 healthcare professionals (67 males and 98 females) at Bambino Gesù Children’s Hospital.
Blood samples were collected prior to immunisation (T0) and 22–30 days post-vaccination (T1).
Antibody titers for H1N1, H3N2, B/Phuket, and B/Austria were quantified by ELISA-based
microneutralization methods. Serum testosterone and 17β-estradiol concentrations were measured
via ELISA, and their correlations with antibody titers were examined using linear regression and
non-parametric analyses. Vaccination history, comorbidities, and adverse events data were collected
by standardised questionnaires and analysed using GraphPad Prism v10. Females exhibited
consistently elevated seroconversion and seroprotection rates for all four influenza viruses in
comparison to males. The greatest seroprotection was noted for the B/Phuket and B/Austria strains,
whereas seroconversion was most significant for H1N1. Correlation tests indicated no statistically
significant relationships between testosterone levels and antibody titres for any strain; however,
negative trends implied a suppressive effect of testosterone on immunological response. Oestradiol
exhibited a robust, substantial positive connection with antibody titers for the B/Phuket strain in
females (ρ=0.4939, P<0.0001), indicating a sex-specific hormonal modulation of immunity.
Previous vaccination history affected antibody responses differently in males and females,
suggesting a cumulative immunological priming effect that differed by sex. Post-vaccination
adverse effects were modest and more prevalent among persons with comorbidities. This research
illustrates gender-specific variations in influenza vaccine responses and proposes hormonal
influence on immune function. The results underscore the necessity of incorporating sex, hormonal
status, and demographics in the formulation of personalised vaccination programs.